When working in environments laden with dust, fumes, air borne bacteria, mists, etc. it is common to wear a powered air-purifying respirator or other type of respiratory protection device. Powered air-purifying respirators protect wearers from such health threatening conditions as asbestos-countering dusts, radionuclides, blood borne pathogens, etc.
A typical powered-air respiratory system will include a head cover having a face shield and a belt-worn air filter unit which provides a flow of filtered air to the head cover via a breathing tube. The air filter unit will contain within its housing a filter such as a high efficiency particulate air (HEPA) filter or other type of filter for filtering out the impurities in the environment. During operation, ambient air is drawn through the belt-mounted air filter unit by a conventional blower motor/impeller assembly (hereinafter referred simply as the "blower motor assembly"). The unfiltered air is then drawn through the air unit's internal filter and the filtered air is then sent into the head cover.
In order to maintain the effectiveness of the respiratory system in filtering out impurities, it is critical that the disposable filter located in the air filter unit be replaced on a periodic basis. Failure to replace the filter on a timely basis causes the system to provide less than optimal filtering capability and can endanger the health of the respiratory system users.
Businesses such as those that have many personal respiratory systems for use by their employees will typically have a maintenance schedule which notifies them when each of the filters in each respiratory unit needs to be replaced. Although effective most of the time, this type of scheduled maintenance approach requires monitoring via a schedule which may or may not be followed on a timely basis. A bigger problem occurs if a filter from one respiratory system is exchanged with a filter from another system or with a previously used filter. In this particular situation, one may lose track of when to replace the particular filter since the filters are no longer associated with the same powered air unit. This situation may cause a filter to stay in service long after it has reached its end-of-life condition and has lost some or all of its filtering capabilities.
Although the above discussion has highlighted the problems associated with personal respiratory systems, the same problems can occur with any filtering device or system that uses a replaceable or portable filter. For example HVAC (heating/ventilation/air conditioning) systems, liquid filtering systems such as water purification systems for electronic assembly plants, automotive air and cabin filters, etc.
Given the portable nature of most filters used in personal respiratory systems and other types of fluid (e.g., air, gas and liquid) filtering devices/systems, a person who is changing a replaceable filter is usually never certain of how much life is left in the filter unless he installs a new filter straight from its original packaging. Otherwise, it could very well be that the filter that is being installed had been previously used elsewhere for some period of time. In these situations, it becomes very difficult to gauge a filter's end-of-life and determine when the filter should be changed. Using a filter beyond its useful life can cause all sorts of problems depending on the type of filtering system in question. For example, in the case of machinery, using a filter beyond its useful life can cause the machinery to prematurely fail. While in respiratory systems, a used-up filter can subject the user to serious health problems. A need thus exists in the art for a filter and system which can overcome the problems stated above.